Are thetford valves “one-way”?

[fluxcap]

Sorry for what may be a dumb question, but do thetford valves only seal in one direction?

I installed a new valve in my black tank (1977 argosy minuet). It works great as far as holding back the “stuff” in the black tank. However, minuets don’t have a grey tank for the shower water. And as I drove home some of the leftover water in the shower plumbing sloshed it’s way to the termination cap, which was capped. And as it backed up to the backside of the black valve, it leaked out through the hole in the valve where the handle rod comes through.


After I noticed it, I did a test and put the termination cap back on and then poured about 2 gallons down the shower and it again backed up to the black valve and poured out through the handle hole.

Is this normal? Seems like if it’s that easy for water to slip out that hole, then there could possibly be leaks there when pulling the handle and dumping (though I didn’t experience any on this trip).

Thanks!
Eric

[uncle_bob]

Hi

The normal waste valves are "two way" in the sense you describe. When closed they will not let "stuff" out or in.

Bob

[fluxcap]

Thanks! I didn’t remember the old valve doing this, but wasn’t sure. I’m going to investigate it more on my next day off, and see if I can figure out why it’s happening. This simple valve replacement has been nothing but a headache, haha.